Spark Plug Upgrade for Turbo RX-8
08-30-2009, 03:48 PM
#1
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Spark Plug Upgrade for Turbo RX-8
I'm tuning a turbo RX-8 for the first time and noticed he had very old stock plugs which need to be replaced. I was wondering what the stock heat ranges for the RX-8 are? I'm assuming its the same as the FD RX-7's with 7 leading and 9 trailing.
I've been trying to figure out what would be considered as an upgrade to stock plugs. I use the Greddy Racing Plug Pro (NGK Iridium R7420's) with 9 leading and 10 trailing in my RX-7. I was considering get these same plugs for for the leading only in 9's and leave the stock trailing there as I heard its a different length and the trailing doesn't do much of the work anyway.
Any ideas/suggestions?
thewird
I've been trying to figure out what would be considered as an upgrade to stock plugs. I use the Greddy Racing Plug Pro (NGK Iridium R7420's) with 9 leading and 10 trailing in my RX-7. I was considering get these same plugs for for the leading only in 9's and leave the stock trailing there as I heard its a different length and the trailing doesn't do much of the work anyway.
Any ideas/suggestions?
thewird
Last edited by thewird; 08-30-2009 at 03:57 PM.
08-30-2009, 04:40 PM
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Is there any reason not to use the RX-8 plug on the trailing? An iridium plug generally has a stronger spark then a platinum one. I don't really like the whole spacer idea either in case the owner goes to another mechanic who has no idea.
thewird
thewird
08-31-2009, 01:59 AM
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08-31-2009, 04:20 PM
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Oh, just making sure. So its the same as the RX-7 and the only reason people use the rx-7 plug is to get it colder with the trailing since its the same size.
thewird
thewird
08-31-2009, 10:03 PM
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That's how I've always pictured it but NGK seems to explain it better...
Let's make this really simple: when you need your engine to run a little cooler, run a colder plug. When you need your engine to run a little hotter, run a hotter spark plug. However, NGK strongly cautions people that going
to a hotter spark plug can sometimes mask a serious symptom of another problem that can lead to engine damage. Be very careful with heat ranges. Seek professional guidance if you are unsure.
With modified engines (those engines that have increased their compression) more heat is a by-product of the added power that normally comes with increased compression. In short, select one heat range colder for every 75-100 hp you add, or when you significantly raise compression. Also remember to retard the timing a little and to increase fuel enrichment and octane. These tips are critical when adding forced induction (turbos, superchargers or nitrous kits), and failure to address ALL of these areas
will virtually guarantee engine damage.
An engine that has poor oil control can sometimes mask the symptom temporarily by running a slightly hotter spark plug. While this is a "Band-Aid" approach, it is one of the only examples of when and why one would select
a hotter spark plug.
to a hotter spark plug can sometimes mask a serious symptom of another problem that can lead to engine damage. Be very careful with heat ranges. Seek professional guidance if you are unsure.
With modified engines (those engines that have increased their compression) more heat is a by-product of the added power that normally comes with increased compression. In short, select one heat range colder for every 75-100 hp you add, or when you significantly raise compression. Also remember to retard the timing a little and to increase fuel enrichment and octane. These tips are critical when adding forced induction (turbos, superchargers or nitrous kits), and failure to address ALL of these areas
will virtually guarantee engine damage.
An engine that has poor oil control can sometimes mask the symptom temporarily by running a slightly hotter spark plug. While this is a "Band-Aid" approach, it is one of the only examples of when and why one would select
a hotter spark plug.
In my opinion I think the stock RX-8 plugs (7-9 heat range) are not suitable for turbo application as the renesis is a high compression motor (10:1) compared to the FD motor (9:1). Mostly I think the issues is with the leading as it needs to be colder. That is why people use the stock FD trailing plug in the leading since its a 9 heat range spark plug and is relatively inexpensive.
thewird
Last edited by thewird; 08-31-2009 at 10:06 PM.
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